1 HEAT OVEN TO 350°F (325°F FOR DARK OR NONSTICK PAN). SPRAY BOTTOM AND SIDES OF 13×9-INCH PAN WITH BAKING SPRAY WITH FLOUR.
2 IN MEDIUM BOWL, STIR TOGETHER FLOUR, 1/2 CUP BROWN SUGAR AND THE SALT. WITH PASTRY BLENDER OR FORK, CUT IN BUTTER UNTIL MIXTURE IS CRUMBLY. SET ASIDE.
3 IN ANOTHER MEDIUM BOWL, GENTLY STIR TOGETHER APPLE MIXTURE INGREDIENTS; SET ASIDE.
4 IN LARGE BOWL, BEAT CAKE INGREDIENTS WITH ELECTRIC MIXER ON LOW SPEED 30 SECONDS, THEN ON MEDIUM SPEED 2 MINUTES, SCRAPING BOWL OCCASIONALLY. POUR INTO PAN.
5 SPREAD APPLE MIXTURE EVENLY OVER CAKE BATTER. SPRINKLE TOPPING EVENLY OVER TOP.
6 BAKE 30 TO 35 MINUTES OR UNTIL TOOTHPICK INSERTED IN CENTER COMES OUT CLEAN. COOL COMPLETELY, ABOUT 30 MINUTES.